A sealant is usually used to prevent the penetration of substances or pollutants (such as air, gas, dust, fire, smoke or liquid) from one location through a barrier into another. Typically, desirable properties of sealants include insolubility, corrosion resistance, and adhesion. Sealants are used in many industries including in agriculture and in home gardening, typically for preventing moisture from penetrating through barriers. For example, the inside of terra-cotta plant pots may include a layer of sealant to reduce water loss from the pot.
Plant pots are commonly used by nurseries and green houses to grow plants for commercial use. Plants are grown in pots until they are mature enough to be distributed to retail outlets or to consumers. Typically, molded plastic pots are used for growing plants. Consumers that purchase plants in pots usually transplant the plants into soil at their home, discarding the plastic pot. The pots then end up in landfills or garbage dumps, where they remain for a very long time because they are not biodegradable.
Alternatives to conventional plastic pots exist. Biodegradable pots made of paper (cellulose fibers), peat and other organic waste are known. These pots are designed to degrade relatively quickly when buried in soil. This allows consumers to simply bury the pot with the plant in it, rather than having to remove the plant from the pot before planting. However, the biodegradable pots must also be substantially resistant to saturation by liquids so that they do not begin to disintegrate prior to being buried in soil.
Some biodegradable pots include a thermoplastic polymer layer which faces an interior of the plant pot which is exposed to soil placed in the plant pot. However, methods of irrigation and the humid environment in many nurseries cause the external surfaces of pots to be exposed to moisture, so that a sealant on the interior of a plant pot does not prevent degradation of the pot while still on the shelf in the nursery.
Nurseries also use plug trays for plant transplants. In plug trays each transplant grows in an individual cell avoiding competition among plants and providing uniformity of the plants. Several other advantages of plugs (also called rooting plugs) over bare-root transplants include a smaller amount of water required for plugs over bare-root transplants, a mechanical multiple-row plug transplanter can be used for planting, there is minimal root damage during transplanting and plant survival is greater. The growing media in plug trays is typically a soilless mix generally made up of a combination of peat, vermiculite and horticultural perlite and sometimes fertilizer which is packaged in a thin degradable wrap. Sometimes adhesives are used for supporting and hardening the plugs.
Some commercial greenhouses use seepage irrigation (also known as sub-irrigation), which is a method of irrigation that allows the soil to be moistened from below the plants' root zone. Water is delivered from below, absorbed upwards, and the excess collected for recycling. Typically, a solution of water and nutrients floods a container or flows through a trough for a short period of time, 10-20 minutes, and is then pumped back into a holding tank for reuse. The bottom parts of plant pots and plugs irrigated this way are almost constantly submerged in water.
Known bio-degradable plant pots and plugs are not suited for use with seepage irrigation systems and many other irrigation systems used in green houses and nurseries since they are susceptible to disintegration while still in the nursery or green house due to exposure to the extreme moisture in green house and nursery environments.